1. Technical Field
The present invention relates to a laser radar device, particularly to a laser radar device that can measure a distance to an object with high accuracy.
2. Related Art
A technology in which a radar device incorporated in a vehicle detects a vehicle in a traveling direction or a passing lane or a distance to an object to control vehicle motion according to the detected distance is becoming widespread.
In a principle of the radar device, light is projected from a light projection part to a monitoring area, the light reflected from an object in the monitoring area is received, and a distance to the object is obtained from light projection timing and light receiving timing.
Conventionally the in-vehicle radar device is frequently placed near a front end of a vehicle body. On the other hand, nowadays the in-vehicle radar device is occasionally placed inside a windshield (see Japanese Unexamined Patent Publication No. 8-160123).
There has been proposed a system in which, in order to cover the wide monitoring area of the object, the light is projected from the light projection part while the projected light is changed in various directions, or the direction of the projected light is widened without changing the light projection direction (see Japanese Unexamined Patent Publication No. 7-253461).
There has been proposed a technology for providing a light shielding wall between the light projection part and light receiving part, which are provided adjacent to each other, to prevent the light projected by the light projection part from being directly received by the light receiving part (see Japanese Unexamined Patent Publication No. 2007-333592).
In the case that the light shielding wall disclosed in Japanese Unexamined Patent Publication No. 2007-333592 is applied to the laser radar device placed inside the windshield, the light reflected from the windshield in the light projected by the light projection part may be projected to a dashboard, and the light projected to the dashboard may be irregularly reflected and possibly received as a noise by the light receiving part.